Silicone rubber compositions comprising bismuth oxide and articles made therefrom

Abstract

The present invention provides novel filled silicone compositions comprising a nano-particulate metal oxide filler selected from nano-particulate monoclinic alpha-phase bismuth oxide, nano-particulate erbium oxide, and mixtures thereof. The new composite compositions exhibit a combination of outstanding performance characteristics in both the cured and uncured states. Thus, the uncured formulations are typically free flowing liquids which are self-leveling, which de-gas readily under vacuum, are readily colorable through the addition of pigments, and which cure at temperatures of about 60° C. The cured compositions possess outstanding acoustic characteristics which make them ideally suited for use in applications such as acoustic lenses for medical imaging and therapy. For example, the acoustic impedance of compositions provided by the present invention is closely matched to the acoustic impedance of human tissue. This may result in an enhancement of ultrasound transmission efficiency between the lens of an ultrasound probe comprising such a composition and the patient.

1. An ultrasonic probe comprising:
 (a) a substrate material; 
 (b) a piezoelectric transducer; and 
 (c) an acoustic lens; 
 said acoustic lens comprising a filled silicone composition comprising a silicone resin and a nano-particulate monoclinic alpha-phase bismuth oxide. 
 
     
     
       2. The ultrasonic probe according to  claim 1 , wherein the nano-particulate alpha-phase bismuth oxide has an average particle size of from about 10 nanometers to about 200 nanometers. 
     
     
       3. The ultrasonic probe according to  claim 1 , wherein the nano-particulate alpha-phase bismuth oxide comprises from about 0.1volume percent to about 15 volume percent of a total volume of the composition. 
     
     
       4. The ultrasonic probe according to  claim 1 , wherein said filled silicone composition further comprises nano-particulate erbium oxide. 
     
     
       5. The ultrasonic probe according to  claim 1 , wherein said filled silicone composition further comprises a pigment. 
     
     
       6. The ultrasonic probe according to  claim 1 , further comprising a pigment selected from the group consisting of carbon black, sodium aluminosulfosilicate, manganese ferrite, and iron oxide. 
     
     
       7. An acoustic lens comprising
 (a) a first curved surface; and 
 (b) a second surface 
 said acoustic lens comprising a filled silicone composition comprising a silicone resin and a nano-particulate monoclinic alpha-phase bismuth oxide. 
 
     
     
       8. An ultrasound diagnostic apparatus comprising:
 (a) an ultrasonic probe comprising (i) a substrate material, (ii) a piezoelectric transducer, and (iii) an acoustic lens comprising a filled silicone composition comprising a silicone resin and a nano-particulate alpha-phase bismuth oxide; 
 (b) a signal processing unit; and 
 (c) an image display.